Abstract: With the advance of computing technology, video compression technology, and cellular network infrastructure, rich multimedia applications are dramatically boosted to users. Currently, a deterministic service model has been developed in which a QoS aware network assisted by the deterministic traffic modeling can provide bounded delay and loss free guarantees to video packets. However, the limited memory capacity and access bandwidth of mobile terminals still affect the delivery of pre-stored video contents. Besides, from the cellular network viewpoint, any halfway request for increasing bandwidth may complicate the resource management. Therefore, this paper proposes an Elastically Deterministic Video Traffic Regulator (ED-VTR) to…regulate the video traffic, and then generate a series of monotonically decreasing bandwidth demands which effectively simplify the resource management and satisfy the decoder buffer limitation. Moreover, for preventing possible non-sustained playback due to insufficient decoder buffer space, this study proposes an intelligent video frame skip algorithm to determine the most suitable temporal range for skipping frames. Simulation results reveal that ED-VTR effectively reduces the initial bandwidth demand and the requirement of decoder buffer space, while still maintaining advantages of deterministic services. More importantly, ED-VTR maintains the sustained playback with good picture quality and outperforms traditional schemes in the case of insufficient decoder buffer space.
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Abstract: In modern photonic switching systems, a major problem is the creation of large fabrics that often exceed the capacity of a single IC. Moreover, with modern throughput requirements, it becomes important to adopt fault-tolerant architectures characterized by the features of low propagation delay, regularity in structure, fewer links/switching elements in the network and simple switching element design. In this paper the design criteria of a specific large, strictly nonblocking Extended Generalized Shuffle Network, characterized by uniform topology, are presented. For the new network, different network operating modes are indicated and the corresponding performance in terms of fault-tolerance is…evaluated.
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Abstract: This paper proposes an explicit rate-based end-to-end distributed congestion control mechanism for multimedia traffic in packet switched networks such as the Internet. The network is viewed as a set of sources distributed with feedback from respective destinations and it is modeled as a nonlinear system. The congestion is controlled by adjusting the transmission rates of the sources in response to the feedback information from destination such as the buffer occupancy, packet arrival and service rate, so that a desired performance referenced to as a quality of service (QoS) can be met. The QoS is defined in terms of packet loss…ratio, transmission delay, system power and fairness. The performance and stability of the system is analyzed mathematically. The proposed scheme has been implemented in the NS-2 simulator. Simulation results demonstrate the performance of the scheme to be in agreement with mathematical analysis. The proposed scheme is shown to provide considerable improvements in terms of the QoS metrics over New-Reno TCP (a variant of AIMD: additive increase multiplicative decrease) technique. Since it is end-to-end, no additional router support is necessary, and the proposed methodology can be readily applied to today's Internet, as well as for real-time video and voice data transfer in unicast networks. Finally some information is given as its overhead needed for the proposed scheme.
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Abstract: In this paper, we investigate the problem of Preplanned Recovery with Redundant Multicast Trees (PRRMT) in optical networks. The redundant trees ensure the source node remains connected to all destination nodes for a multicast session request under single edge or node failures. Our objective is to minimize the total number of links used for both trees. We show that PRRMT can be formulated as an integer linear program (ILP), and also develop a heuristic algorithm. The ILP approach and heuristic algorithm are experimentally evaluated on 14-node NSFNET, 21-node Italian network, and a randomly generated 40-node mesh network. From experimental results,…we conclude that: (1) ILP approach leads to optimal solutions for NSFNET and Italian network but does not converge for many instances of arbitrary topologies, (2) Our heuristic algorithm yields optimal or near optimal results in very short time, and (3) The edge-disjoint trees can protect the transmission for an edge failure or a node failure.
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Abstract: We present a comparison between different methods to calculate the equivalent Poisson traffic step used by the Wavelength Decomposition Method. The Wavelength Decomposition Method is used to compute the blocking probabilities in Wavelength Division Multiplexing (WDM) optical networks without wavelength converters. The approach divides the WDM network into layers (colors) and uses a moment matching method to calculate an equivalent Poisson overflow traffic to each layer. A corresponding single link model is developed to match the traffic characteristic for each end-to-end traffic. Analyzing blocking probabilities in each layer of the network is derived from an exact approach. We study Fredericks…and Hayward's, Sanders's, Equivalent Random Traffic ERT, Rapp's, Berkeley's and Bernoulli–Poisson–Pascal BPP moments matching methods. Simulation results are presented to evaluate the accuracy of each method.
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Abstract: In this paper, we present an assessment of the blocking performance in wavelength routed chordal ring networks. The performance is focused on chord lengths of w=3, w=N/4, and $w=\sqrt{N}+3$ , being N the number of nodes. It is shown that, in a 100-node chordal ring network, the use of the chord length of w=N/4 instead of w=3 clearly reduces the blocking probability. A reduction of the blocking probability is also observed when the chord length of $w=\sqrt{N}+3$ is used, instead of w=N/4 or w=3. In fact, the blocking probability gain, due to the choice of the chord…length of $w=\sqrt{N}+3$ instead of w=3, is of the order of 104 for a load per node of 1 Erlang, and of the order of 1010 for a load of 0.1 Erlang, with 16 wavelengths per link in both cases. Concerning the influence of wavelength interchange it is shown that, for low loads per node, the highest blocking gains due to wavelength interchange are obtained with a chord length of 3, and the lowest gains are obtained with a chord length of $w=\sqrt{N}+3$ . However, for higher loads per node an inverse situation is observed. Chordal rings have also been compared with rings and with mesh-torus. This comparison revealed an important feature: very small blocking gains, due to the increase of the nodal degree from 3 (chordal ring with 100 nodes and $w=\sqrt{N}+3)$ to 4 (mesh torus with 100 nodes), were observed. In this case, as the load per node decreases from 5 Erlang to 0.01 Erlang, the variation of the nodal degree gain remains within one order of magnitude for 16 wavelengths per link. Furthermore, small gains were also observed for networks with a larger size (1600 nodes). Thus, if a small blocking performance degradation is allowed, the choice of a chordal ring with $w=\sqrt{N}+3$ , instead of a mesh-torus, leads to a reduction in the number of network links, and hence in the total cable length, since the number of links in a N-node chordal ring is 3×N, and the number of links in a N-node mesh-torus is 4×N.
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Abstract: As the popularity of the new multicast based services like video conferencing and distance learning is gaining significant attention, the network operator's concern to provide such services in an off-line and on-line manner with optimum network resource utilization is increasing rapidly. In recent past, traffic grooming also gained significant importance to handle sub-wavelength level demands in the WDM mesh networks to optimize the network resources. The majority of traffic grooming work addresses issues related to the unicast traffic scenario. We, in this paper, address the problem of routing and wavelength assignment of multicast sessions (MC-RWA) with sub-wavelength traffic demands in…the scenario of WDM mesh networks. We deal with two scenarios where the traffic demands are either static or dynamic. Individual nodes need to have the capability of duplicating traffic in order to support multicast traffic grooming. So, we propose a node architecture, which performs the task of traffic duplication in the optical as well as in the electronic domain. This architecture is cost effective as it allows the duplication in optical domain also. The traffic duplication at the electronic level is much more expensive than at the optical level. In static scenario, we study the problem of assigning routes and wavelengths to the multicast sessions so as to minimize the total electronic copying cost at the nodes. We present a non-linear programming (NLP) formulation as an analytical model for the problem. As solving the model for large network is intractable, we propose three heuristic algorithms namely k-SPT, GRS, and GCOT. In dynamic scenario, we study the problem with the objective of reducing the blocking of dynamically arriving requests using the proposed technique called maximizing the minimum freeload (MMFL). We have conducted extensive simulation experiments to demonstrate the effectiveness of the proposed schemes.
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